CD33-CD123 IF-THEN gating reduces toxicity while enhancing the specificity and memory phenotype of AML-targeting CAR-T cells.

CAR T-cell therapy has remarkably succeeded in treating lymphoblastic leukemia. However, its success in AML remains elusive due to the risk of on-target off-tumor toxicity to hematopoietic stem and progenitor cells (HSPC) and insufficient T-cell persistence and longevity. Using a SynNotch circuit, we generated a high-precision "IF-THEN" gated logical circuit against the combination of CD33 and CD123 AML antigens and demonstrated anti-tumor efficacy against AML cell lines and patient-derived xenografts. Unlike constitutively expressed CD123 CAR-T cells, those expressed through the CD33 SynNotch circuit could preserve HSPCs and lower the risk of on-target off-tumor hematopoietic toxicity. These gated CAR-T cells exhibited lower expression of exhaustion markers (PD1, Tim3, LAG3, and CD39), higher frequency of memory T cells (CD62L+CD45RA+), and enhanced expansion. While targeting AML, the moderated circuit CAR signal also helped to mitigate cytokine release syndrome, potentially addressing one of the ongoing challenges in CAR-T immunotherapy.